Put iPhone in recovery mode

– charge your iPhone
– disconnect iPhone from computer (remove usb cable)
– turn off iPhone completely (wait until iPhone screen turns black)

– start iTunes 7.6
– push and hold the home button on iPhone
– while holding the home button connect the usb cable to iPhone
– (iPhone will start up doing this = Apple logo)
– continue holding the home button
– after a while you’ll see the Connect To iTunes image on the iPhone:

– release the home button

– iTunes will popup this window:

– press Check, wait a little…

– NOW iPhone is in recovery mode:

– press OK

– now you can use shift/option and restore whatever firmware you want using iTunes

thanks to geircito at hackint0sh.org